1. Field of the Invention
The present invention relates to an amphibious, all terrain type (ATV) vehicle, such as for example a marsh craft, and more particularly to a tracked ATV utilized for travel over different types of terrain, such as swamps, bogs and the like, and for travel cross-country with obstacles of different character, with various degrees of inclination.
2. Prior Art
Various types of amphibious crafts or ATV's are known in the art. One commonly known and cited is U.S. Pat. No. 2,546,523 issued Mar. 27, 1951 to Reynolds which described a marsh buggy vehicle comprising a pair of spaced, elongated pontoons disposed and secured in a parallel relationship, two endless chains passing about each pontoon over sprockets mounted on transverse, driven shafts. The chains were joined together transversely by slats which form the threads for the craft.
Another example of an amphibious marsh vehicle is shown in U.S. Pat. No. 3,842,785 issued Oct. 22, 1974 to Rivet. The apparatus described by Rivet included two pontoons, with two endless drive chains carried in channels disposed on top and bottom of the pontoons. The cleats attached to the chains have plastic blocks which are secured to the web of the cleats and bear against the top and bottom of the pontoons.
These and other similar vehicles have a number of operating problems, one of the most common of which is chain wear. In operation the chain is exposed to the mud, sand and water, and to prolong the chain life it is a common practice to lubricate the elements of the chain in places of connection. But any lubricant applied to a chain has a tendency to catch and collect dirt and sand, which causes rapid wear of the chain elements, particularly between the carrier roller and pin.
To solve this problem some inventors have come up with the idea of using rubber belts instead of metal chains, as for example in U.S. Pat. No. 3,217,687 issued Nov. 16, 1965 to Erkelson et al., which describes an amphibious vehicle having endless belts provided for operation mainly in water when the belts are substantially submerged.
But such vehicles face another problem when traveling on the ground, this problem being commonly known as "chain" or "track throw," which arises from the inability of many such designs to provide efficient means for securing a chain or a belt in its place over the driving sprockets or wheels.
Additionally, many "marsh buggies" have had the problem of "track sag," which further adds to the problem of track throw.
These problems have been known in the art for a long period of time and, to prevent rapid wear of the elements, a number of solutions have been suggested. In some cases special pads are attached to the sides of a chain in order to reduce friction and thus to eliminate the problem. While these and other solutions have proven to be satisfactory to some extent, they still have not provided full reliability.
Other prior patents showing other exemplary amphibious type vehicles are listed below:
______________________________________ Patentee(s) U.S. Pat. No. Issue Date ______________________________________ J. A. Dorst 2,068,664 Jan. 26, 1937 J. M. Hait 2,404,489 July 23, 1946 B. A. Swennes 2,487,397 Nov. 8, 1949 F. F. Reynolds 2,546,523 March 27, 1951 H. L. Prosser 3,108,564 Oct. 29, 1963 A. H. Pitchford 3,299,849 Jan. 24, 1967 F. B. Gregg 3,418,961 Dec. 31, 1968 M. E. Hebert 3,474,751 Oct. 28, 1969 L. H. Roy 3,487,802 Jan. 6, 1970 M. E. Hebert 3,611,979 Oct. 12, 1971 A. V. Brusacoram 3,760,763 Sept. 25, 1973 ______________________________________